What is the test for establishing necessity in a defence case?

The requirement to establish necessity has special meaning. For simple convenience I adopt the description provided in the Crown Pre-Hearing Brief as it appears to fairly lay out that law by reference to the authorities: The principle of necessity implies that since we will lose entirely the benefit of the evidence unless it is received untested by cross-examination, there is a greater or lesser necessity of receiving it in order correctly to dispose of the litigation. As the court held in R v. Khelawon [2006 SCC 57]: “[t]”he criterion of necessity is founded on society’s interest in getting at the truth. Because it is not always possible to meet the optimal test of contemporaneous cross-examination, rather than simply losing the value of the evidence, it becomes necessary in the interests of justice to consider whether it should nonetheless be admitted in hearsay form”. Necessity refers to the necessity of the hearsay evidence to prove a fact in issue not the necessity to the prosecution’s case. The criterion of necessity must be given a flexible definition, capable of encompassing diverse situations. The focus is on the quality of the evidence proposed to be admitted, when compared to what may be otherwise available. If there is no other way to present the same or similar evidence, then necessity is easily made out. It is important to note that the criteria of necessity and reliability work in tandem; if the reliability of the evidence is sufficiently established, the necessity requirement can be relaxed. (Footnotes omitted) (at p. 25)